Apparatus for collecting samples from drum dryers for determining drying curves



Jan. 13, 1970 J. WADSWORTH ETAL 3,488,791

APPARATUS FOR COLLECTING SAMPLES FROM DRUM DRYERS FOR Filed Sept. 8, 1967 DETERMINING DRYING CURVES 4 Sheets-Sheet 1 INVENT OR JAMES L WADSWORTH ALEXANDER S. GALLO JAM-ES J. SPADARO ATTORNEY J. I. WADSWORTH ETAL 9 a 8 M B S AW 3 3 m S e R h E S 4 Jan. 13, 1970 APPARATUS FOR COLLECTING SAMPLES FROM DRUM DRY DETERMINING DRYING CURVES Flled Sept 8, 1967 ATTORNEY FOR Jan. 13, 1970 J. l. WADSWORTH ETAL APPARATUS FOR COLLECTING SAMPLES FROM DRUM DRYERS DETERMINING DRYING CURVES 4 Sheets-Sheet 5 Filed Sept. 8. 1967 FIG.4

INVENTORS mwwm JAMES JEgAD/mo ATTORNEY J. l. WADSWORTH COLLECTING SAMPL Jan. 13, 1970 3,488,791

APPARATUS FOR ES FROM DRUM DRYERS FOR DETERMINING DRYING CURVES 4 Sheets-Sheet 4 Filed Sept. 8, 1967 INVENTORS JAMES I-WADSWORTH ALEXANDER S- GALLO JAMES J. SPADARO [/j ue/\.

ATTORNEY QUE United States Patent APPARATUS FOR COLLECTING SAMPLES FROM DRUM DRYERS FOR DETERMINING DRYING CURVES James I. Wadsworth and Alexander S. Gallo, Metairie, and James J. Spadaro, New Orleans, La., assignors to the United States of America as represented by the Secretary of Agriculture Filed Sept. 8, 1967, Ser. No. 667,327 Int. Cl. F26b 5/14, 17/28 U.S. Cl. 15256.51 1 Claim ABSTRACT OF THE DISCLOSURE A detachable auxiliary doctor assembly, with positioning flexibility is added to drum dryer systems. Its purpose is to provide a device for collecting samples of processed material being dried, for a plurality of drying times, without disturbing the normal operation of the drum dryer system; thereby also providing a method for determining drying-time curves on drum dryers without varying the speed of rotation of the drums.

A non-exclusive, irrevocable, royalty-free license in the invention herein described throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to a roll and doctor blade operational assembly improvement. Specifically this invention relates to a roll and doctor blade assembly improvement for equipment such as drum dryers and the like, in which the assembly can be removable at will, and provides positioning flexibility. In addition, the invention permits location of the doctor blade at any of a select number of locations along the working surface of the roll. The invention is particularly useful in drum dryer operations.

The main object of this invention is to provide a means of obtaining drying data for more efiicient operation of drum dryers and the like.

During experimental drying studies data is collected relating the moisture content of the product to drying time. This data is usually presented in the form of dryingrate curves where the drying rate (dw/d0) is plotted against time (0) or moisture content (w). The rate curves show that the drying process is not one in which a single mechanism controls throughout but one which is divided into several periods where the drying rate is subject to variation with time or moisture content. These drying curves are particularly valuable in analyzing the operation of dryers from the standpoint of improving performance and increasing capacity.

For some types of dryers it is difiicult to collect the data necessary to determine drying rate curves. This is especially true in reference to drum dryers because of the variation in film thickness with drum speed.

In order to properly determine drying rate information, it is necessary that all drying parameters except time remain constant. Standard drum dryers are made so that the position of the scraper knife (doctor blade) is fixed relative to the drum, and the only available means of varying drying time is to vary the speed of rotation of the drum. It was found that on drum dryers, because of the mechanisms involved in the adherence of a film of material on the drum surface, the thickness of this film varied with variation in the speed of rotation of the drum, thus making it impossible to vary drying time without affecting film thickness.

It was possible to compensate for changes in film thickness caused by variation in drum speed by varying other parameters which affect the mechanisms involved in the adherence of material to the drum surface. This, however, was a very tedious and time-consuming process because there are no means available to objectively measure the thickness of a semifiuid film on a hot revolving drum surface. Therefore, it was necessary to collect the product over a period of time and back-calculate film film thickness from production rate, product moisture, feed moisture, feed density, and drum speed. When a change was made in drying time by varying drum speed, it required several attempts at varying other parameters affecting film thickness in order to return film thickness to its original value, and, because of the procedure involved and the fact that steady-state conditions have to be re-established before any meaningful data can be collected, it can readily be seen that this was an unsatisfactory situation. Also, this situation was not compatible with the requirements that all drying parameters except time be held constant, and onecannot be certain that other factors affecting drying rate, such as the physical structure of the film, have not been changed by the variation of parameters which was necessary to obtain the desired film thickness.

We have found that we can overcome this problem by providing those skilled in the art with a simple device and a method of obtaining drying data and thereby improve the operation of such machines. This device is in the form of a detachable, flexible positioning doctor blade assembly. Variations may be made to suit any particular dryer onto which it would fit. However, the basic idea I is to provide a plurality of positions from which the doctor blade assembly performs its function.

For illustrating the device which is part of this invention, we refer to the following figures. These figures illustrate the adaptation of the invention to an American pilot-plant model double-drum dryer which is a typical dryer. This, however, should not be construed as limiting the invention.

FIGURE 1 is a side elevation view showing the doctor blade bar supports in closed position, and by dashed lines, in an open position.

FIGURE 2 is a cross section taken on line 2-2 of FIGURE 1 and is an auxiliary view of the clamps which secure the bar supports in a closed position.

FIGURE 3 is a side elevation schematic view, showing the positioning of the doctor blade assembly in relation to One drum of a double-drum dryer which the doctor blade would serve.

FIGURE 4 is a front elevation schematic view showing the doctor blade in a midway position.

FIGURE 5 is a perspective view of the doctor blade assembly in respect to the drying drum, shown when disengaged.

Referring to the drawings wherein like numerals identify similar parts throughout, it can be seen that the doctor blade assembly supports 2, 3, 4, 5 are four in number, consisting of a pair of outer supports 2, 4 and a pair of inner supports 3, 5. The inner supports are fixed by a plurality of tie rods 6 to the base plate 1, which, in turn, is secured to the dryer frame bed 16 by wing bolt 17. The outer supports are attached to the base plate 1 by pivoting studs 7 which supports are held in place by washers 13 and lock nut 12. It can be seen in FIGURE 1 that the inner and outer supports 3, 5, and 2, 4 complement each other upon total closure. The closed assembly would be held in a closed position by swing bolts 9, which are secured to swing bolt lug 10 by swing bolt wing nut 11. Swing bolt lug 10 is welded to outer support 2, 4. The detail of the said swing bolt 9 including lug and swing nut arrangement can be seen in FIG. 2. The closed assembly 3 describes an arc of about 155. The tie rods 6 and lock nuts 14 as shown in FIGURE 1, hold the doctor blade supports 2, 3, 4, in a rigid position.

It should be noted that, when the outer supports 2 and 4 are closed against the inner supports 3 and 5 with the doctor blade assembly in place, the doctor blade pivots 8a are held firmly in the selected circular notches 21 and 22, in inner (3, 5) and outer supports (2, 4), and the only allowable movement of the doctor blade assembly is rotational in respect to doctor blade pivots 8a to permit the pressuring of the doctor blade against the surface of the drum. It should be further noted that the notches 21 and 22 do not describe a perfect circle when the supports 2, 3, 4, 5 are closed. Because there is a lateral movement of the outer supports 2, 4 relative to the inner supports 3, 5 when the outer supports 2, 4 are pivoting around pivoting stud 7, it would not be possible to open or close the supports 2, 3, 4, 5 around the doctor blade assembly pivots 8a if the notches 21, 22 formed complete circles. Therefore, the notches 21 on the outer supports 2, 4 must be circular arcs of less than 30. The inner support notches 22, of course, can be as much as 180, since these remain stationary, and do not restrict the movement closure. FIGURE 1 also shows the desired curvature of outer blade supports 2, 4, which is designed to facilitate the opening and closing of the blade assembly support members in the repositioning of the doctor blade assembly.

FIGURE 3 shows the positioning of the doctor blade 19 at an approximate midpoint and at about the last operable position.

FIGURE 4 serves the purpose of illustrating the position of the tie rods 6 which support the doctor blade assembly 8 approximately at the midpoint in respect to the available notch range. This view also shows a schematic position of the drum 20 in respect to the doctor blade assembly 8. The weight of the doctor blade assembly, as well as ease in positioning, makes it desirable to have at least two handles 18 for manipulating. These rod-type handles are very convenient; however, the handles can be designed to operate in a suitable manner which would not necessarily change the instant invention.

FIGURE 5 is a perspective view of the doctor blade assembly engaged in position against an ordinary drum dryer. This figure shows lateral spacing of the bar supports, which cannot be appreciated from the other views.

In the operation of the movable doctor blade apparatus it is extremely important that the edge of the doctor blade be parallel to the drum axis. To accomplish this fine adjustment the leveling bolts 23 shown in FIGURE 5 are required. When the proper adjustment is obtained, the leveling bolts 23 are locked in place by lock nuts 24.

The spacing bars 25 are used to properly position the movable doctor :blade apparatus relative to the drum such that the circular are formed by the doctor blade assembly supports 2, 3, 4, 5 is concentric with the drum 20. Spacing bar screws 26 are used to attach spacing bars 25 to the base plate 1.

The main advantage of using the device which is the instant invention is the speed and ease with which data can be obtained for drying rate curves. In operation, that is, in obtaining drying data during normal operation of a drum dryer or roll machine, the assembly is relocated in various positions by loosening the wing nuts 11 on the swing blots 9, swing the bolts out of the lug slots, and while supporting the doctor blade assembly the outer supports 2 and 4 are opened and the blade assembly 8 located in the desired position. The outer segments 2 and 4 are then closed and clamped in position by swing bolts 9, and secured by wing nut 11, against welded lug 10. Downward hand pressure on the handles 18 of the blade assembly 8 will cause the doctor blade edge 19a to come in contact with the drum 20, thereby scraping processed material off into a suitable container (not shown) for moisture determination. The knife edge 19a is depressed momentarily against the drum surface so that a sample can be collected without disturbing dryer equilibrium. The action is repeated as above, a number of times equal to or less than the number of available notches 21, 22 in the assembly, whenever the relocation of the blade assembly 8 is desired.

The time required to collect samples for a complete drying curve is about from 5 to 10 minutes of time. It is possible, in a relatively short period of time, to collect samples for a series of drying curves for various steam pressures, drum velocities, film thicknesses, and feed compositions.

We claim:

1. In a drum dryer system having an adjustable, main doctor blade positioned adjacent a dryer drum to remove dried material therefrom and a main framework constituting main doctor blade and drum support means, the improvement which comprises a detachable auxiliary doctor blade assembly mounted on said framework, said auxiliary doctor blade assembly comprising:

(a) an auxiliary doctor blade having round, shaft-like extensions at each end; and

(b) curved auxiliary doctor blade support means conforming to the curved surface of the dryer drum pivotally mounted on an auxiliary framework secured to the main framework and positioned to enable the auxiliary doctor blade to contact the surface of the drum, said auxiliary doctor blade support means comprising:

(1) a first pair of jaw members each independently pivotable about separate parallel axes, each of said parallel axes being parallel to the axis of the dryer drum,

(2) a second pair of jaw members similar to said first pair and separated from said first pair by a distance comprising about the width of the auxiliary doctor blade, the opposed edges of each pair of jaw members having a plurality of matched flutes cut in their respective edges to accommodate the shaft-like extensions on the auxiliary doctor blade, whereby the doctor blade can be positioned in any desired location around the periphery of the drum independently of the main doctor blade, and

(3) means for clamping the members of each pair of jaws to retain the auxiliary doctor blade at any desired location and angle with respect to the surface of the drum.

References Cited UNITED STATES PATENTS 2,596,215 5/1952 Crosland l5-256.51 X 2,929,155 3/1960 Overton 341 12 FOREIGN PATENTS 1,208,643 9/1959 France.

557,051 5/ 1958 Canada.

WALTER A. SCHEEL, Primary Examiner LEON G. MACHLIN, Assistant Examiner U.S. Cl. X.R. 

